The fact that you watched the power on your radio go off and on makes me think you might have a "ground" issue. All electrical life starts with a solid ground system. Job #1 is to freshen them. And also clean and verify both battery cables. Plenty of time to consider more complex issues after that.
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Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea, and the investment of your time in this procedure is always well worth it!
You can't tell much of anything by looking at ground connections!! You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. Be sure to remove all paint from any ground connections.
Start with the one on the back corner of the head, and where it attaches to the firewall, as it deteriorates over time and is an area that makes it susceptible to damage. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.
Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.
If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support.
